Skeleton member structure

ABSTRACT

A skeleton member structure having a tubular structural member ( 11, 211 ) filled with granular materials for absorbing impact energy. The granular materials includes a granular material having a hollow portion ( 12   a,    212   a ) or a porous granular material. When the skeleton member receives an impact, the granular materials are deformed or collapsed, and impact energy is stably absorbed. Since the granular materials are hollow or porous, the weight of the skeleton member filled with the granular materials is reduced.

TECHNICAL FIELD

This invention relates to a skeleton member structure which is impartedwith improved shock absorbing capability without increasing its weight.The invention also relates to a method for forming solidified granularmaterials.

BACKGROUND ART

Skeleton member structures having skeleton or structural members filledwith filling materials are know from, for example, (1) paperpre-published for 2001 JSAE (Society of Automotive Engineers of Japan)Spring General Meeting, entitled “ATTEMPT TO COPE WITH BOTHCRASHWORTHINESS AND WEIGHT REDUCTION” (hereinafter called Prior Art 1),(2) science paper, 1986, The university of Manchester, England, “STATICAND DYNAMIC AXIAL CRUSHING OF FOAM-FILLED SHEET METAL TUBES”(hereinafter called Prior Art 2), (3) paper published in AutomobileEngineering, Vol. 55, April, 2001, “DEVELOPMENT OF A METHOD OF ENHANCINGBODY FRAME STRENGTH USING STRUCTURAL FOAM” (hereinafter called Prior Art3), (4) Japanese Patent Laid-Open Publication No. 2001-130444 entitled“IMPACT ENERGY ABSORBING MEMBER” (hereinafter called Prior Art 4), and(5) Japanese Patent Laid-Open Publication No. 2000-46106 entitled“DAMPING PANEL” (hereinafter called Prior Art 5).

Methods for forming solidified granular materials are know from, forexample, (6) U.S. Pat. No. 4,610,836 entitled “METHOD OF REINFORCING ASTRUCTURAL MEMBER” (hereinafter called Prior Art 6), (7) the art forsolidifying a granular material by use of a resin material (hereinaftercalled Prior Art 7), (8) the art for solidifying a granular material bya crosslinking liquid film (hereinafter called Prior Art 8), and (9) theart for solidifying a granular material in itself (hereinafter calledPrior Art 9).

Prior Art 1 is directed to the art of filling the skeleton member of anautomobile with a foamed filling material to realize weight reductionwhile ensuring absorption energy during a collision.

In Prior Art 2, FIG. 3( b) (ii) at pp. 301 shows an example in which atube of square cross section filled with polyurethane foam is deformed.

Prior Art 3 discloses the art of filling a part of the interior of aframe with a foamed resin to restrain local buckling deformation of theframe by dispersing the energy of a collision.

(4) Prior Art 4 describes in paragraph [0025] at page 4 that “in orderthat the impact energy absorbing member can easily receive an impactload in the surface direction thereof, in the case where the impactenergy absorbing member has a cavity portion, it is preferable thatfitting matter such as grains, a foamed material or a core be fittedinto the interior of the impact energy absorbing member to enhance thelongitudinal rigidity of the impact energy absorbing member”. Inaddition, FIG. 14 of the same publication discloses an impact energyabsorbing member having an interior in which fitting matter is fitted.

(a) and (b) of FIG. 1 of Prior Art 5 illustrate a damping panel which isfilled with a mixture of high rigidity grains and low elastic grains forabsorbing vibration energy according to elastic deformation.

FIG. 2 of Prior Art 6 illustrates a structure in which a skeleton memberis filled with adhesive-coated glass microspheres wrapped in cloth madeof glass fiber. U.S. Pat. No. 4,695,343 also discloses a similarstructure.

Prior Art 7 will be described below with reference to FIGS. 27 and 28hereof.

FIG. 27 shows a structural member 402 in which a skeleton member 400which constitutes a skeleton structure is filled with a solidifiedgranular material 401.

The solidified granular material 401 shown in FIG. 28 is made ofgranular materials 403 and a resin material 404 with which the spacesamong the granular materials 403 are filled to solidify the granularmaterials 403.

Prior Art 8 will be described below with reference to FIG. 29 hereof.

The solidified granular material 410 shown in FIG. 29 has a structure inwhich adjacent ones of the granular materials 403 are bonded to oneanother by a crosslinking liquid film 411. In the formation of thisbonding structure, after moisture or the like has been added to thegranular materials 403, the granular materials 403 are pressed andheated to form the crosslinking liquid film 411, thereby forming thesolidified granular material 410.

The solidified granular material 420 shown in FIG. 30 is matter in whichadjacent ones of the granular materials 403 are bonded to one another bymelting the surfaces of the granular materials 403. Reference numeral421 denotes a solidified portion in which the surfaces of the granularmaterials 403 are solidified after having been melted.

Prior Arts 1 to 3 have a structure in which a skeleton member is filledwith a foamed material, but has the following problem. This problem willbe described below with reference to the graphs shown in FIGS. 20A and20B.

FIG. 20A is a graph for explaining the relationship between the foamingratio of a foamed material and the buckling load at which bucklingoccurs when a compressive load is applied to a structural member in theaxial direction thereof, and the vertical axis represents the bucklingload and the horizontal axis represents the foaming ratio. According tothis graph, when the buckling load of the structural member is to beincreased, it is necessary to reduce the foaming ratio.

FIG. 20B is a graph for explaining the relationship between the foamingratio of the foamed material and the weight of the structural member,and the vertical and horizontal axes represent the weight and thefoaming ratio, respectively. According to this graph, as the foamingratio is made smaller, the weight of the structural member increases.

It can be seen from these graphs that in the range of foaming ratios nothigher than a foaming ratio at which a predetermined buckling load b isensured (in the foamed-material effective area shown in FIG. 20B), theweight becomes large and a reduction in the weight of the structuralmember becomes difficult.

Crush tests of structural members which are respectively filled with thefoamed materials disclosed in the aforementioned Prior Arts 1 to 3 andthe grains disclosed in Prior Art 4, for example, solid powder will bedescribed below with reference to FIGS. 21A, 21B and 21C.

In FIG. 21A, an axial compressive load P as shown by an arrow is appliedto a structural member 300 having a tubular skeleton member 300 a filledwith a foamed material or solid grains, thereby forcedly deforming thestructural member 300.

In FIG. 21B, letting λ be the amount of deformation of the structuralmember 300, and as the amount of deformation λ increases, the structuralmember 300 is buckled and deformed into the Z-shaped or dogleg-shapedconfiguration shown in FIG. 21B.

FIG. 21C is a graph for explaining the relationship between the amountof deformation λ and the load P with the structural member 300 deformedas described above, and the vertical and horizontal axes represent theload P and the amount of deformation λ, respectively. In addition, threekinds of samples are used: a sample A which has an interior not filledwith a filling material and uses only a skeleton member, a sample Bfilled with a foamed material, and a sample C filled with solid grains.

When the amount of deformation λ is small, the sample B (filled with afoamed material) generates a larger load than the sample A, and as theamount of deformation λ becomes larger, the load P sharply decreases.

Regarding the sample C (filled with solid grains), as the amount ofdeformation λ becomes comparatively larger, the load P sharplydecreases. This is because in each of the samples B and C, since thefoamed material or the solid grains are not easily crushed in an earlystage of deformation, the internal pressure of the structural memberexcessively rises and is buckled into a Z-shaped or dogleg-shapedconfiguration and the load P is sharply decreased by this buckling.

Then, a crush test of the structural member of Prior Art 5 that isfilled with high rigidity grains and low elastic grains will bedescribed below with reference to FIGS. 22A, 22B and 22C.

In FIG. 22A, the structural member 301 is a member in which a tubularskeleton member 301 a is filled with a multiplicity of low elasticgrains 302 and a multiplicity of high rigidity grains 303. First, theload P which is an axial compressive load is applied to the structuralmember 301, thereby forcedly deforming the structural member 301. As aresult, the low elastic grains 302 are gradually deformed as shown inFIG. 22B. When the amount of deformation λ of the structural member 301reaches L, the low elastic grains 302 are nearly completely crushed, andthen the load P directly acts on the high rigidity grains 303.

FIG. 22C is a graph for explaining the relationship between the amountof deformation λ of the structural member and the load P when thestructural member 301 is deformed as described above, and the verticaland horizontal axes represent the load P and the amount of deformationλ, respectively. In addition, the sample A shown by a solid lineincludes only the skeleton member shown in FIG. 21C, and a sample Dshown by a dashed line is the structural member 301 described withreference to FIGS. 22A and 22B.

The load P of the sample D is nearly equal to that of the sample A untilthe amount of deformation λ reaches L, but when the amount ofdeformation λ exceeds L, the load P sharply increases. This is because,as described above, when the amount of deformation λ exceeds L, the loadP acts on the high rigidity grains which are hardly crushed, and theload P sharply increases. When the load P is made to act further, thesample D is buckled and deformed into a Z- or doglegged-shape similar tothat shown in FIG. 21B, and the load P sharply decreases.

Then, a bending test of a structural member filled with a fillingmaterial will be described with reference to FIGS. 23A to 23F.

FIG. 23A shows the state in which a structural member 300B having theskeleton member 300 a filled with a foamed material (the sample B shownin FIG. 21C) is supported at two supporting points 306, 306. δ denotesthe amount of deformation of the structural member 300B to which a loadis applied (the definition of δ is the same in the followingdescription).

FIG. 23B shows the fact that the skeleton member 300 a of the structuralmember 300B is filled with a foamed material 308.

In FIG. 23C, when a load W is applied to the structural member 300B in adirection perpendicular to the axis of a structural part 3200B, i.e., inthe direction of an arrow, the structural member 300B is bentdownwardly.

As shown in FIG. 23D, the granular materials 308 between a top side 311and a bottom side 312 of the skeleton member 300 a are compressed andlateral sides 313 and 314 of the structural member 300 a are swollenoutwardly, whereby the lateral sides 313 and 314 peel off the foamedmaterial 308.

As shown in FIG. 23E, when the load W is further applied to thestructural member 300B, the structural member 300B is further deformed,and as shown in FIG. 23F, the structural member 300B is crushed to afurther extent in the vertical direction, and the lateral sides 313 and314 are swollen sideways to a further extent.

As shown in FIGS. 23D and 23F, as deformation proceeds, the lateralsides 313 and 314 of the skeleton member 300 a peel off the foamedmaterial 308, so that the foamed material 308 becomes unable to easilyrestrain the deformation of the structural member 300B.

Then, a bending test of a skeleton member filled with solid grains willbe described with reference to FIGS. 24A to 24F.

FIG. 24A shows the state in which a structural member 300C having theskeleton member 300 a filled with solid grains (the sample C shown inFIG. 21C) is supported at two supporting points 306, 306.

FIG. 24B shows the fact that the structural member 300 a is filled withsolid grains 317.

As shown in FIG. 24C, when the load W is applied to the structuralmember 300C in a direction perpendicular to the axis of the structuralmember 300C, i.e., in the direction of a white arrow, the structuralmember 300C is bent downwardly. As shown in FIG. 24D, the solid grains317 between the top side 311 and the bottom side 312 of the structuralmember 300 a are compressed and the lateral sides 313 and 314 of theskeleton member 300 a are swollen outwardly, whereby the solid grains317 spread sideways according to the swelling of the lateral sides 313and 314.

As shown in FIG. 24E, when the load W is further applied to thestructural member 300C, the structural member 300C is further deformedand the bottom side of the structural member 300C is broken. Namely, asshown in FIG. 24F, the structural member 300C is crushed to a furtherextent in the vertical direction and the lateral sides 313 and 314 areswollen sideways to a further extent, so that the internal pressurebecomes excessively large and the bottom side 312 is broken.

Accordingly, when the skeleton member 300 a is broken, the flexuralrigidity of the structural member 300C becomes extremely low.

FIGS. 24A to 25F show a bending test of a structural member having askeleton member filled with low elastic grains and high rigidity grains.

FIG. 25A shows the state in which the structural member 301 the skeletonmember 301 a filled with low elastic grains and high rigidity grains(the sample D shown in FIG. 22C) is supported at the two supportingpoints 306, 306.

FIG. 25B shows the fact that the skeleton member 301 a is filled withthe low elastic grains 302 and the high rigidity grains 303.

As shown in FIG. 25C, when the load W is applied to the structuralmember 301 in a direction perpendicular to the axis of the structuralmember 301, i.e., in the direction of an arrow, the structural member301 is bent downwardly, and as shown in FIG. 25D, the load acts on thelow elastic grains 302 and the high rigidity grains 303 between the topside 311 and the bottom side 312 of the skeleton member 301 a, and thelow elastic grains 302 are shrunk and the lateral sides 313 and 314 ofthe skeleton member 301 a are swollen outwardly, whereby the low elasticgrains 302 and the high rigidity grains 303 spread sideways according tothe swelling of the lateral sides 313 and 314.

As shown in FIG. 25E, when the load W is further applied to thestructural member 301, the structural member 301 is further deformed andthe bottom side of the structural member 301 is broken. Namely, as shownin FIG. 25F, the structural member 301 is crushed to a further extent inthe vertical direction and the lateral sides 313 and 314 are swollensideways to a further extent, so that the internal pressure becomesexcessively large and the bottom side 312 is broken.

Accordingly, when the skeleton member 301 a is broken, the flexuralrigidity of the structural member 301 becomes extremely low.

The results of the conventional structural members filled with therespective filling materials are shown in the graph of FIG. 26. FIG. 26shows the results of the sample A and the samples B to D shown in FIGS.23 to 25. The vertical axis represents the load W applied to thestructural member, while the horizontal axis represents the amount ofdeformation δ.

The load W of the sample B is generally large with respect to that ofthe sample A, but as the amount of deformation δ increases, the load Wgradually decreases.

In the case of the sample C and the sample D, the value of the load Wincreases in an early stage of deformation, but since the load W sharplydecreases while the amount of deformation δ is small, the maximum amountof deformation δ is small.

Absorption energy capable of being absorbed by a structural memberduring a vehicle collision is nearly equivalent to the result obtainedby, letting δ be a small amount of deformation, integrating the load Wcorresponding to this small amount of deformation from zero to maximumin terms of the amount of deformation δ, i.e., the area below each ofthe curves. Accordingly, if the load W for each value of the amount ofdeformation δ can be maintained at a large value and the maximum amountof deformation δ can be increased, the absorption energy of thestructural member during the collision can be made large. In addition,if the load W can be made constant, impact energy can be stableabsorbed.

In the case of the above-described sample B, the maximum amount ofdeformation δ is large, but the load W for each value of the amount ofdeformation δ is not sufficiently large, whereas in the case the samplesC and D, the maximum load W is large, but the maximum amount ofdeformation δ is small. Accordingly, any of the samples B to D is smallin total absorption energy, i.e., cannot sufficiently absorbe impactenergy.

In the case of the sample C and the sample D, the variation of the loadW is large, so that the absorption of impact energy does not stabilize.

In the structure disclosed in Prior Art 6, since individual microspheresare bonded together by an adhesive, solid matter having high rigidity inwhole can be formed. However, for example when an impact acts on askeleton member, if the deformation of each of the microspheres issmall, load occurring in the skeleton member sharply increases, so thatimpact energy cannot be sufficiently absorbed.

In Prior Art 7, as shown in FIGS. 27 and 28, since the granularmaterials 403 are solidified by the resin material 404, the rigidity ofthe structural member 402 increases, but the amount of the resinmaterial 404 becomes large to increase the weight of the structuralmember 402.

In Prior Art 8, as shown in FIG. 29, the mutual bonding of the granularmaterials 403 by the crosslinking liquid film 411 is based on surfacetension, so that bonding force is weak and a large solidified granularmaterial is difficult to form as the solidified granular material 410.

In Prior Art 9, as shown in FIG. 30, the granular materials 403 aresolidified by melting the surfaces of the granular materials 403themselves, so that adjacent ones of the granular materials 403 can befirmly bonded to one another. However, in the case where the granularmaterials 403 are ceramics, for example, glass, silicon dioxide (SiO₂)and aluminum oxide (Al₂O₃: alumina), the granular materials 403 must beheated at a very high temperature. In addition, since special equipmentis needed, it is not easy to form the solidified granular material 420.

Accordingly, there is a demand for a skeleton member structure capableof stable absorbing more impact energy in spite of an restrainedincrease in weight.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided askeleton member structure characterized by a skeleton member andgranular materials having hollow portions or porous granular materials,a space inside the skeleton member and/or a space surrounded by theskeleton member and a surrounding panel member being filled with thegranular materials.

When the space is to be filled with the granular materials, preferably,the space is directly filled with the granular materials or a fillingmember previously filled with the granular materials is fitted into theskeleton member.

The skeleton member preferably includes a plurality of frames, sidesills, cross members, pillars, beams and rails all of which are used foran automobile.

An increase in the weight of the skeleton member can be restrained bythe granular materials having the hollow portions or the porous granularmaterials. When the skeleton member receives an impact, owing to thefrictional force among the granular materials and the deformation or thecollapse of the granular materials themselves, the deformation of theskeleton member can be made to proceed gradually from a load-acting sideand smoothly while a large load is being generated, whereby far largerimpact energy can be absorbed more stable.

It is preferable that the skeleton member structure further includessecond granular materials, and adjacent ones of the second granularmaterials are bonded to one another by the hollow first granularmaterials. The first granular materials are made of a resin material.The second granular materials may also be solid, and is preferablyformed of hollow or porous granular materials.

Since the second granular materials are bonded to one another by thehollow first granular materials, the weight of the skeleton memberstructure can be reduced. In addition, the mutual bonding of the secondgranular materials can be made firm, and when the skeleton memberreceives impact, the first granular materials can be collapsed, wherebyit is possible to highly efficiently absorb far more impact energy.

According to another aspect of the present invention, there is provideda method for forming a solidified granular material fitted in a skeletonmember and/or in a spaced surrounded by the skeleton member and asurrounding panel member, which method is characterized by a step ofmixing first granular materials which are hollow and made of a resin,and second granular materials, and a step of bonding adjacent ones ofthe second granular materials to one another via the first granularmaterials by melting surfaces of the first granular materials.

The first granular materials and the second granular materials can befirmly bonded to one another by melting the surfaces of the firstgranular materials which are hollow and made of a resin, whereby it ispossible to form a lightweight large-sized solidified granular material.In addition, the surfaces of the resin-made first granular materials canbe melted at a low temperature, whereby the solidified granular materialcan be easily formed without the need for special equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a skeleton member structure according toa first embodiment of the present invention;

FIG. 2 is a magnified cross-sectional view taken along line 2-2 of FIG.1;

FIGS. 3A to 3D show the crushed state of a structural member accordingto the first embodiment of the invention;

FIGS. 4A, 4B and 4C are views showing the deformed state in a crush testof the structural member of the first embodiment, and FIGS. 4D and 4Eare views showing the deformed state of a comparative example;

FIGS. 5A to 5F are views showing the deformed state in a bending test ofthe structural member of the first embodiment;

FIGS. 6A and 6B are perspective views showing portions of a vehicleskeleton structure to which the vehicle skeleton structure according tothe invention is to be applied;

FIGS. 7A to 7E are cross-sectional views showing a plurality of examplesin each of which the vehicle skeleton structure according to theinvention is adopted in the front side frame of a vehicle.

FIGS. 8A to 8D are cross-sectional views showing a plurality of examplesin each of which the vehicle skeleton structure according to theinvention is adopted in the rear frame of the vehicle;

FIGS. 9A to 9F are cross-sectional views showing a plurality of examplesin each of which the vehicle skeleton structure according to theinvention is adopted in the center pillar of the vehicle;

FIGS. 10A to 10E are cross-sectional views showing a plurality ofexamples in each of which the vehicle skeleton structure according tothe invention is adopted in the roof side rail of the vehicle;

FIGS. 11A to 11G are views showing a plurality of embodiments of agranular material according to the first embodiment;

FIG. 12 is a graph showing the results of crush tests of structuralmembers according to the invention as well as comparative examples;

FIG. 13 is a graph showing energy absorption efficiencies in the crushtests of structural members according to the invention;

FIG. 14 is a graph showing the results of bending tests of structuralmembers according to the invention as well as comparative examples;

FIG. 15 is a cross-sectional view of a solidified granular materialdisposed to fill the skeleton member according to the second embodimentof the invention;

FIG. 16 is a magnified view of part of the solidified granular materialshown in FIG. 15;

FIGS. 17A and 17B are views showing the state of deformation of thesolidified granular material shown in FIG. 15 when a load is appliedthereto;

FIGS. 18A and 18B are, respectively, a view of the state in which a loadis applied for performing a crush test of the structural member havingthe skeleton member filled with the solidified granular material shownin FIG. 15, and a graph showing the result of the crush test and acomparative example;

FIG. 19 is a graph showing the weight of the structural member filledwith the solidified granular material shown in FIG. 15, together withcomparative examples.

FIG. 20A is a graph showing the relationship between foaming ratio andbuckling load when a compressive load is axially applied to aconventional structural member having a skeleton member filled with afoamed material, and FIG. 20B is a graph showing the relationshipbetween the foaming ratio and the weight of the structural member;

FIGS. 21A and 21B show the state of deformation of a conventionalstructural member having a tubular skeleton member filled with a foamedmaterial or solid grains when a compressive load is applied to theconventional structural member in the axial direction, and FIG. 21C is agraph showing the relationship between the amount of deformation of thestructural member and the compressive load;

FIGS. 22A and 22B show the state of deformation of a conventionalstructural member having a tubular skeleton member filled with lowelastic grains and high rigidity grains when a compressive load isapplied to the conventional structural member in the axial direction,and FIG. 22C is a graph showing the relationship between the amount ofdeformation of the structural member and the compressive load;

FIGS. 23A to 23F are views showing the state of deformation of aconventional structural member having a skeleton member filled with afoamed material when a load is applied to perform a bending test on thestructural member;

FIGS. 24A to 24F are views showing the state of deformation of aconventional structural member having a skeleton member filled withsolid grains when a load is applied to perform a bending test on thestructural member;

FIGS. 25A to 25F are views showing the state of deformation of aconventional structural member having a skeleton member filled with lowelastic grains and high rigidity grains when a load is applied toperform a bending test on the structural member;

FIG. 26 is a graph showing the result of the bending tests of theconventional structural members having the skeleton member filled withthe respective filling materials;

FIG. 27 is a cross-sectional view of a structural member having askeleton member filled with a conventional solidified granular material;

FIG. 28 is a magnified cross-sectional view of the conventionalsolidified granular material shown in FIG. 27;

FIG. 29 is a cross-sectional view showing the state in which granularmaterials are bonded to one another by a conventional crosslinkingliquid film; and

FIG. 30 is a cross-sectional view showing the state in which granularmaterials are bonded to one another by melting the surfaces of theconventional granular materials.

DETAILED DESCRIPTION OF THE INVENTION

The structural member 10 shown in FIG. 1 corresponds to a member whichforms the skeleton or frame structure of a vehicle, and is a samplewhich is fabricated for testing purposes to grasp the impact energyabsorbing performance of the vehicle skeleton structure.

As shown in FIG. 2, the structural member 10 is made of a skeletonmember 11 having a tubular shape and a plurality of hollow granules orgranular materials 12 with which the skeleton member 11 is filled.Reference numeral 12 a denotes a hollow portion. The granular materials12 are considerably small compared to the skeleton member 11, but, inFIG. 2, are shown at a magnified scale for the convenience ofdescription. The skeleton member 11 includes end-closing members 13 and13 as shown in FIG. 1.

Silicon dioxide (SiO₂), aluminum oxide (Al₂O₃: alumina), silica alumina,resin, glass or ceramics is suitably used as the granular materials 12.

FIGS. 3A to 3D show the state in which the structural member accordingto the invention is crushed.

FIG. 3A shows the state in which a load P which serves as an axialcompressive load is applied to the structural member 10 to deform thestructural member 10. The amount of displacement of the structuralmember 10 at this time is λ.

FIG. 3B shows the cross-sectional state of the structural member 10before the axial compressive load is applied to the structural member10.

As shown in FIG. 3C, when the load is applied to the structural member10, adjacent ones of the granular materials 12 are brought into strongcontact with one another and travel while generating large frictionalforces, so that large resistance occurs due to the deformation of thestructural member 10.

As shown in FIG. 3D, when the load continues to be applied, smalldeformation and collapse (12 b denotes collapsed pieces resulting fromthe collapse of the granular materials 12) occurs in the granularmaterials 12 in the structural member 10 on the side on which the loadis acting, and restrains a sharp increase in the internal pressure ofthe skeleton member 11, whereby Z-shaped or dogleg-shaped bucklingdeformation can be prevented from occurring in the skeleton member 11.

FIGS. 4A to 4E show deformed states of structural members in crush teststhereof. FIGS. 4A, 4B and 4C show an embodiment of the invention, andFIGS. 4D and 4E show a comparative example. First, the embodiment willbe described.

FIG. 4A shows a state before deformation. As shown in FIG. 4B, when theload P which serves as an axial compressive load is applied to thestructural member 10 in the state of FIG. 4A, the granular materials 12start to be deformed to a small extent at one end side (i.e., the topside) where the load P to the structural member 10 is applied, finallyresulting in the collapse of the granular materials 12. Contrarily,deformation hardly occurs at the other end side (i.e., the bottom side)of the structural member 10.

As shown in FIG. 4C, when the load P continues to be applied, the smalldeformation and collapse of the granular materials 12 described abovewith reference to FIG. 4B gradually proceeds downwardly, and thestructural member 10 are nearly regularly and smoothly deformed into abellows-like shape.

Then, the comparative example will be described.

FIG. 4D shows a state before deformation of a structural member 221which is the sample C shown in FIG. 24F (a structural member filled withsolid grains). As shown in FIG. 4E, when the load P which serves as anaxial compressive load is applied during the state of FIG. 4D, solidgrains 217 with which the structural member 221 is filled are hardlycrushed and the load P sharply increases, so that the structural member221 start to be buckled and deformed into a dog-leg-like shape or aZ-like shape (not shown). After that, the load P sharply decreases.

As described above, in the embodiment of the invention, since thestructural member 10 is crushed in order from one end thereof, thestructural member 10 can ensure a large amount of displacement whileretaining a nearly constant large reaction force, and can highlyefficiently absorb energy applied to the structural member 10.

On the other hand, in the comparative example, the load P becomesexcessively large in an early stage of deformation, and when thestructural member 221 is buckled and deformed into a Z-like ordog-leg-like shape, the load P sharply decreases, so that the structuralmember 221 cannot effectively absorb energy which accompaniesdeformation.

FIGS. 5A to 5F show a bending test of the structural member according tothe invention.

FIG. 5A shows the state in which the structural member 10 is supportedat two supporting points 15, 15. δ denotes the amount of deformation ofthe structural member 10 to which a load is applied.

FIG. 5B shows a cross section of the state in which the structuralmember 10 is filled with the granular materials 12.

As shown in FIG. 5C, when a load W is applied to the structural member10 in the direction of an arrow, the structural member 10 is deflecteddownwardly, and as shown in FIG. 5D, the granular materials 12 between atop side 17 and a bottom side 18 of the structural member 10 arecompressed and lateral sides 21 and 22 of the structural member 10 areswollen outwardly, whereby the granular materials 12 travel sideways.

As shown in FIG. 5E, when the load W is further applied to thestructural member 10, the structural member 10 is further deformed, andas shown in FIG. 5F, the structural member 10 is crushed to a furtherextent in the vertical direction, and the lateral sides 21 and 22 areswollen sideways to a further extent. The granular materials 12 in thevicinity of the top side 17 are collapsed by a pressure rise in theinterior of the structural member 10, whereby an excessive pressure risecan be prevented.

Accordingly, unlike the prior art, damage to the skeleton member due toa pressure rise inside the structural member does not occur, and theload W shown in FIG. 5E can be prevented from sharply lowering.

FIGS. 6A and 6B show portions of the vehicle skeleton structureaccording to the invention, to which the above-described structuralmember is to be applied.

As shown in FIG. 6A, the skeleton structure according to the inventionis applied to front side frames 31, 31 disposed below the oppositelateral sides of an engine located in the front portion of a vehiclebody, side sills 38, 38 disposed below the opposite lateral sides of avehicle chamber, a front floor cross member 58 passed between left andright side sills 38, 38, center pillars 75, 75 erected from therespective side sills 38, 38, and rear frames 61, 61 extended rearwardlyfrom the respective side sills 38, 38.

Furthermore, as shown in FIG. 6B, the skeleton structure according tothe invention is applied to left and right front pillars 73, 73, frontdoor beams 89 and rear door beams 95 respectively provided in left andright front doors 89 a and left and right rear doors 95 a, left andright roof side rails 96, 96 provided on the opposite lateral sides of aroof, and roof rails 117, 118 passed between the left and right roofside rails 96, 96.

FIGS. 7A to 7E respectively show first to fifth examples in each ofwhich the vehicle skeleton structure according to the invention isadopted in a front side frame. In front side frames 31A to 31D accordingto the first to fourth examples, their skeleton members are directlyfilled with the granular materials 12, and in a front side frame 31Eaccording to the fifth example, a filling member previously filled withthe granular materials 12 is fitted in its skeleton member.

The front side frame 31A according to the first example shown in FIG. 7Aconstitutes a skeleton member 34 which is formed of an outer panel 32and an inner panel 33 which is provided closer to an engine room than tothis outer panel 32. This skeleton member 34 is filled with the granularmaterials 12. When the front side frame 31A is to be filled with thegranular materials 12, the front side frame 31A may be filled with thegranular materials 12 in whole along the length thereof, or the frontside frame 31A may be filled with the granular materials 12 in partalong the length thereof; that is to say, two separating walls may beprovided in the front side frame 31A in such a manner as to be spacedwith a predetermined distance part from each other in the longitudinaldirection and the space between these two separating walls may be filledwith the granular materials 12. Portions which will be described latermay be similarly constructed.

The front side frame 31B according to the second example shown in FIG.7B constitutes a skeleton structure 44 which is formed of an outer panel32 having an inclined surface 37 and an inner panel 33 which is providedcloser to the engine room than to the outer panel 32 and has an inclinedsurface 42. This skeleton structure 44 is filled with the granularmaterials 12.

The front side frame 31C according to the third example shown in FIG. 7Cconstitutes a skeleton structure 48 which is formed of an outer panel32, an inner panel 33 and a separating wall 47 which is secured to theinside of each of these outer panel 32 and inner panel 33. Of a firstchamber 51 and a second chamber 52 which are separated from each otherby the separating wall 47 between the outer panel 32 and the inner panel33, the first chamber 51 is filled with the granular materials 12.

In the front side frame 31D according to the fourth example shown inFIG. 7D, the second chamber 52 of the front side frame 31C shown in FIG.7C is filled with the granular materials 12.

The front side frame 31E according to the fifth example shown in FIG. 7Eis a member representative of an example in which a filling member 57 inwhich the granular materials 12 are previously enclosed is fitted in theinside of the skeleton member 34. Namely, the skeleton member 34 isfilled with the granular materials 12 via the filling member 57.

FIGS. 8A to 8D show first to fourth examples in each of which thevehicle skeleton structure according to the invention is adopted in arear frame. In each of rear frames 61A to 61D which are the first andsecond examples, the skeleton member is directly filled with thegranular materials 12.

In the rear frame 61A which is the first example shown in FIG. 8A, thereis shown an example in which the space between a lower panel 62 and arear floor panel 63 provided at a position above this lower panel 62 isfilled with the granular materials 12.

In the rear frame 61B which is the second example shown in FIG. 8B,there is shown an example in which the space between the lower panel 62and a sub-lower panel 66 secured at a position above the lower panel 62is filled with the granular materials 12.

In the rear frame 61C which is the third example shown in FIG. 8C, thereis shown an example in which the space between the sub-lower panel 66secured at a position above the lower panel 62 shown in FIG. 8B and arear floor panel 63 provided at a position above this sub-lower panel 66is filled with the granular materials 12.

In the rear frame 61D which is the third example shown in FIG. 8D, thereis shown an example in which a filling member 72 is disposed in thespace surrounded by the lower panel 62 and the rear floor panel 63 andthe filling member 72 is filled with the granular materials 12.

FIGS. 9A to 9F show first to sixth examples in each of which the vehicleskeleton structure according to the invention is adopted in a centerpillar. In each of center pillars 75A to 75E which are the first tofifth examples, the skeleton member is directly filled with the granularmaterials 12 in a non-solidified state, and in a center pillar 75F whichis the sixth example, there is shown an example in which a filler memberpreviously filled with the granular materials 12 is fitted in theskeleton member.

In the center pillar 75A which is the first example shown in FIG. 9A,there is shown an example in which an skeleton member 78 is formed of anouter panel 76 and an inner panel 77 which is disposed on the vehiclechamber side of this outer panel 76 and the skeleton member 78 isdirectly filled with the granular materials 12.

The center pillar 75B which is the second example shown in FIG. 9B is askeleton member 80 formed by securing a reinforcing member 79 betweenthe outer panel 76 and the inner panel 77. The space between thereinforcing member 79 and the outer panel 76 is filled with the granularmaterials 12.

In the center pillar 75C which is the third example shown in FIG. 9C,there is shown an example in which the space between the reinforcingmember 79 shown in FIG. 9B and the inner panel 77 is filled with thegranular materials 12.

In the center pillar 75D which is the fourth example shown in FIG. 9D,there is shown an example in which a center pillar garnish 84 is securedto the vehicle chamber side of the skeleton member 78 and the spacebetween this center pillar garnish 84 and the skeleton member 78 isdirectly filled with the granular materials 12.

In the center pillar 75E which is the fifth example shown in FIG. 9E,there is an example in which a center pillar garnish 91 provided with aplurality of ribs 87, 88 are secured to the vehicle chamber side of theskeleton member 78 and the space between the center pillar garnish 91and the skeleton member 78 is filled with the granular materials 12.

In the center pillar 75F which is the sixth example shown in FIG. 9F,the center pillar garnish 84 is secured to the vehicle chamber side ofthe skeleton member 78 and a filling member 94 which is previouslyfilled with the granular materials 12 is fitted in the space betweenthese center pillar garnish 84 and skeleton member 78.

FIGS. 10A to 10E show first to fifth examples in each of which thevehicle skeleton structure according to the invention is adopted in aroof side rail. In each of roof side rails 96A to 96E which are thefirst to fifth examples, the skeleton member is directly filled with thegranular materials 12.

The roof side rail 96A which is the first example shown in FIG. 10Aconstitutes a skeleton member 101 which is formed of an outer panel 97and an inner panel 98 disposed at the vehicle chamber side of this outerpanel 97. This skeleton member 101 is directly filled with the granularmaterials 12.

The roof side rail 96B which is the second example shown in FIG. 10B isa skeleton member 105 which is constructed in such a manner that areinforcing member 104 is secured between the outer panel 97 and theinner panel 98. The space between the reinforcing member 104 and theouter panel 97 is directly filled with the granular materials 12.

In the roof side rail 96C which is the third example shown in FIG. 10C,there is shown an example in which the space between the reinforcingmember 104 shown in FIG. 10B and the inner panel 98 is directly filledwith the granular materials 12.

In the roof side rail 96D which is the fourth example shown in FIG. 10D,there is shown an example in which a roof-side rail garnish 111 issecured to the vehicle chamber side of the skeleton member 101 and thespace between the roof-side rail garnish 111 and the skeleton member 101is directly filled with the granular materials 12.

In the roof side rail 96E which is the fifth example shown in FIG. 10E,there is shown an example in which the roof-side rail garnish 111 shownin FIG. 10D is provided with a plurality of ribs 114 and the spacebetween this roof-side rail garnish 111 and the skeleton member 101 isdirectly filled with the granular materials 12.

FIGS. 11A to 11G show a plurality of other examples of a granularmaterial according to the invention.

A granular material 122 which is the first example shown in FIG. 11A isa porous indefinite granular material which forms an indefinite shapeand has a plurality of independent hole portions 121.

In the second example shown in FIG. 11B, there is shown a porousindefinite granular material 125 having a plurality of hole portions 124which communicate with one another.

In the third example shown in FIG. 11C, there is a porous definite (inFIG. 11C, elliptic) granular material 127 having the plurality ofindependent hole portions 121.

In the fourth example shown in FIG. 11D, there is a porous definite (inFIG. 11D, elliptic) granular material 131 having the plurality ofindependent hole portions 124 which communicate with one another.

In the fifth example shown in FIG. 11E, there is shown a granularmaterial 134 having a star-like external shape with a hollow portion133.

In the sixth example shown in FIG. 11F, there is shown a pipe-shapedgranular material 136.

In the seventh example shown in FIG. 11G, there is shown a sphericalgranular material 137 having a hollow portion 138.

FIG. 12 is a graph showing the results of crush tests of structuralmembers according to the invention, and the vertical axis represents theload P which is an axial compressive load, while the horizontal axisrepresents the amount of deformation λ according to axial compression.

An embodiment 1 is a structural member filled with hollow granularmaterials. An embodiment 2 is a skeleton member filled with porousgranular materials (the granular materials 122 shown in FIG. 11A). Acomparative example 1 is a structural member which is a sample A made ofonly the skeleton structure shown in FIG. 16C that is not filled with afilling material. A comparative example 2 is a structural member whichis the sample C shown in FIG. 16C and filled with solid grains. Acomparative example 3 is a structural member which is the sample B shownin FIG. 16C and filled with a foamed material.

As compared with the comparative examples 1 to 3, in the embodiment 1and the embodiment 2, the load P does not sharply increase in an earlystage of deformation, and it is possible to stably maintain a large loadP and also to obtain a large amount of deformation λ. Namely, it ispossible to increase the integral of the load P from zero to maximum interms of the amount of deformation λ, whereby it is possible to obtainlarge absorption energy.

FIG. 13 is a graph showing energy absorption efficiencies in the crushtests of structural members according to the invention. Specifically,FIG. 13 comparatively shows the energy absorption efficiency E of eachof the embodiment 1, the embodiment 2, a comparative example 2 and acomparative example 3, where the energy absorption efficiency E of thestructural member of the comparative example 1 that is not filled with afilling material is 1. Incidentally, the energy absorption efficiency Eis a value obtained by dividing absorbed energy by the weight of astructural member.

The energy absorption efficiency E of each of the embodiment 1 and theembodiment 2 is greatly larger than 1, and exhibits the effect of thehollow granular materials and the porous granular materials.

FIG. 14 is a graph showing the results of bending tests of structuralmembers according to the invention, and the vertical axis represents theload W which is made to act perpendicularly to the axis of a structuralmember, while the horizontal axis represents the amount of displacementδ, of the structural member due to the load W.

As the structural members, there are shown the embodiment 1 (hollowgranular materials), the embodiment 2 (porous granular materials), thecomparative example 1 (sample A), the comparative example 2 (sample C)and the comparative example 3 (sample B) all of which have beendescribed with reference to FIG. 12.

In the embodiment 1 and the embodiment 2, it is possible to maintain thelarge load W at a nearly constant level from an early stage ofdeformation to a later stage of deformation, and it is possible toabsorb large energy during deformation.

As described above with reference to FIGS. 2, 9A, 9D and 11A, theinvention is characterized in that the space in the center pillar 75A,or the space surrounded by the center pillar 75A and the surroundingcenter pillar garnish 84, or both the space in the center pillar 75A andthe space surrounded by the center pillar 75A and the surrounding centerpillar garnish 84 are directly filled with the granular materials 12having the hollow portions 12 a and the granular materials 12, or arefitted with a filling member previously filled with the granularmaterials 12 having the hollow portions 12 a and the granular materials12.

Then, a solidified granular material which is disposed to fill astructural member according to a second embodiment of the invention willbe described with reference to FIGS. 15 to 19.

FIG. 15 shows a cross-sectional view of a solidified granular materialdisposed to fill the structural member according to the secondembodiment of the invention. This solidified granular material 215 ismade of hollow resin-made first granular materials 212 and solid secondgranular materials 213. Adjacent ones of the second granular materials213 are bonded to one another by the above-described first granularmaterials 212. Actually, the first granular materials 212 fill thesecond granular materials 213 in a nearly dense state, but are coarselyillustrated for the convenience of description.

FIG. 16 is a magnified view of a solidified granular material accordingto the second embodiment of the invention. The solidified granularmaterial 215 is a member in which adjacent ones of the second granularmaterials 213 are bonded together by melting and then solidifying thefirst granular materials 212. Reference numeral 212 a denotes a hollowportion of the first granular materials 212, and reference numeral 214denotes a solidified portion formed by the solidification of the firstgranular materials 212.

Then, the state in which the above-described solidified granularmaterial 215 is deformed by a load being applied thereto will bedescribed with reference to FIGS. 17A and 17B.

In FIG. 17A, during a vehicle collision, when the load P acts on astructural member 210 from the outside, the load P is transmitted to thesolidified granular material 215 via a skeleton member 211 and thesolidified granular material 215 is deformed as shown in FIG. 17B.

Namely, in an early stage of deformation of the solidified granularmaterial 215, the first granular materials 212 and the second granularmaterials 213 are slightly deformed. As the load is further applied anddeformation proceeds, the deformation of the hollow first granularmaterials 212 becomes larger with the second granular materials 213hardly deformed, and the first granular materials 212 near the portionof the structural member 210 to which the load is applied are collapsed.As the load P further continues to act, the collapse of the firstgranular materials 212 gradually proceeds toward the bottom side of thestructural member 210.

A collapsed portion 212 b resulting from the collapse of the firstgranular material 212 generates large frictional force with an adjacentcollapsed portion 212 b and an adjacent second granular material 213.When the solidified granular material 215 is being deformed, thisfrictional force becomes large resistance and absorbs large impactenergy during the collision. Since the collapse of the first granularmaterials 212 gradually travels, impact energy is stable and efficientlyabsorbed.

FIGS. 18A and 18B show the contents of a crush test of a structuralmember according to the second embodiment. In FIG. 18A, the amount ofdeformation λ of the structural member 210 when the load P which is acompressive load is applied to the structural member 210 in the axialdirection thereof is found. FIG. 18B is a graph showing the relationshipbetween the load P and the amount of deformation λ, and the verticalaxis represents the load P, while the horizontal axis represents theamount of deformation λ.

As shown in FIG. 18B, the comparative example 1 is a structural memberhaving a structural member filled with solid granular materials, and thegranular materials are not solidified. As compared with such comparativeexample 1, in the embodiment which is the structural member 210 fittedwith the solidified granular material 215 (refer to FIG. 15) accordingto the invention, it can be seen that the load P increases compared tothe comparative example 1 and impact energy absorbing performance isimproved.

FIG. 19 is a graph comparatively showing the weight of the structuralmember according to the second embodiment and the weights of comparativeexamples. Assuming that the weight W of the comparative example 1 (thestructural member filled with only the solid granular materials shown inFIG. 18B) is 1, the weight W of the structural member filled with thesolidified granular material 215 (refer to FIG. 2) of the presentembodiment merely slightly exceeds 1, and the increase of the weight issmall with respect to the comparative example 1.

The comparative example 2 is a structural member whose interior isfilled with urethane resin, and the increase of the weight W is largewith respect to the present embodiment.

The second granular materials 213 of the embodiments shown in FIGS. 15,16, 17A and 17B have been described above with reference to solidgranular materials by way of example, but the second granular materials213 in the invention are not limited to solid granular materials and mayalso be those shown in FIGS. 11A to 11G as the first embodiment, forexample, indefinite porous materials, definite porous materials,star-shaped materials having hollow portions, pipe-shaped materials orspherical granular materials having hollow portions.

Accordingly, since the second granular materials 213 are formed ashollow or porous granular materials, a further reduction in the weightof the structural member can be realized in combination with the firstgranular materials 212 (refer to FIG. 15) which bond the second granularmaterials 213.

The solidified granular material 215 according to the second embodimentis adopted in the vehicle skeleton structures shown in FIGS. 6A and 6B.

As described above in connection with FIGS. 15, 17A and 17B, in thefirst place, the invention of these embodiments is characterized in thatin a structure in which the skeleton member 210 and/or the spacesurrounded by the skeleton member 210 and the surrounding panel memberare filled with granular materials, the granular materials are made ofthe hollow first granular materials 212 and the second granularmaterials 213 and adjacent ones of the hollow second granular materials213 are bonded to one another by the first granular materials 212.

By bonding the adjacent ones of the second granular materials 213 to oneanother with the hollow first granular materials 212 in this manner, itis possible to reduce the weight of the structural member 210. Inaddition, the mutual bonding of the second granular materials 213 can bemade firm by the melting of the first granular materials 212.Accordingly, when the skeleton member 210 receives impact, the firstgranular materials 212 are collapsed. The collapsed portion 212 bresulting from the collapse of these first granular materials 212generates large frictional force when the solidified granular material215 is being deformed, whereby large resistance can be obtained toabsorbs larger impact energy. Furthermore, since the collapse of thefirst granular materials 212 gradually travels, impact energy can bestable and efficiently absorbed.

Further, the invention is characterized in that when the skeleton member210 and/or the space between the skeleton member 210 and the surroundingpanel member is to be filled with the solidified granular material 215,the solidified granular material 215 is formed by a step of mixing theresin-made hollow first granular materials 212 and the second granularmaterials 213 and a step of bonding the first granular materials 212 andthe second granular materials 213 by melting surfaces of the firstgranular materials 212.

According to this solidified granular material forming method, it ispossible to firmly bond the first granular materials 212 and the secondgranular materials 213 by melting the surfaces of the resin-made hollowfirst granular materials 212, whereby it is possible to form thelightweight large-sized solidified granular material 215. In addition,the surfaces of the resin-made first granular materials 212 can bemelted at a low temperature, whereby the solidified granular material215 can be easily formed without the need for equipment such as specialheating equipment.

Incidentally, in the invention, when the skeleton member is to be filledwith the solidified granular material, the solidified granular materialmay also be inserted into the skeleton member after having being formedinto a predetermined shape. Otherwise, the solidified granular materialmay be formed by mixing the first and second granular materials, thenfilling the skeleton member with these mixed granular materials, andsubsequently heating the skeleton member.

INDUSTRIAL APPLICABILITY

As described above, according to the invention, an increase in theweight of a skeleton member structure can be restrained by granularmaterials having hollow portions or porous granular materials. When theskeleton member receives impact, owing to the frictional force among thegranular materials and the deformation or the collapse of the granularmaterials themselves, the deformation of the skeleton member can be madeto proceed gradually from a load-acting side and smoothly while a largeload is being generated, whereby far larger impact energy can beabsorbed more stably. Accordingly, the skeleton member structure of theinvention is usefully applicable to skeleton members for railroads,ships, airplanes, motorbikes and the like, and particularly, to skeletonmembers for automobiles.

1. A skeleton member structure comprising: a skeleton member; andgranular materials having hollow portions or being porous, wherein atleast one of a space inside the skeleton member and a space definedbetween the skeleton member and a surrounding panel member is filledwith the granular materials, and wherein the skeleton member includes aplurality of frames, side sills, cross members, pillars, beams andrails, all being for use on an automobile.
 2. The skeleton memberstructure according to claim 1, wherein the granular materials arefilled directly into the space defined by the skeleton member and thesurrounding panel or into a filling member which is fitted into theskeleton member.
 3. A skeleton member structure comprising: a skeletonmember; and granular materials having hollow portions or being porous,wherein at least one of a space inside the skeleton member and a spacedefined between the skeleton member and a surrounding panel member isfilled with the granular materials, and wherein the granular materialsare first granular materials and further comprising second granularmaterials, adjacent ones of the second granular materials being bondedto one another by the first granular materials having hollow portions.4. The skeleton member structure according to claim 3, wherein the firstgranular materials are made of a resin material.
 5. The skeleton memberstructure according to claim 3, wherein the second granular materialsare solid.
 6. The skeleton member structure according to claim 3,wherein the second granular materials comprise hollow or porous granularmaterials.
 7. A method for forming a solidified granular material thatis filled in at least one of a skeleton member and in a space defined bythe skeleton member and a surrounding panel member, the methodcomprising the steps of: mixing first granular materials that are hollowand made of a resin, with second granular materials; and bondingadjacent ones of the second granular materials to one another via thefirst granular materials by melting surfaces of the first granularmaterials.
 8. The skeleton member structure according to claim 1,wherein both the space inside the skeleton member and the space definedbetween the skeleton member and the surrounding panel member are filledwith the granular materials.
 9. The skeleton member structure accordingto claim 8, wherein the granular materials are filled directly into thespace surrounded by the skeleton member or into a filling member whichis fitted into the skeleton member.
 10. A skeleton member structureaccording to claim 8, wherein the granular materials are first granularmaterials and further comprising second granular materials, adjacentones of the second granular materials being bonded to one another by thefirst granular materials having hollow portions.
 11. A skeleton memberstructure according to claim 10, wherein the first granular materialsare made of a resin material.
 12. A skeleton member structure accordingto claim 10, wherein the second granular materials are solid.
 13. Askeleton member structure according to claim 10, wherein the secondgranular materials comprise hollow or porous granular materials.